If I have an Xbox gold membership, do I need an additional gamepass or is the membership enough to be able to use all games and functions to the full?
Gold is for online. Game pass is like netflix for games. Game pass ultimate is both together
So there are different variants, Xbox Live, Xbox Live Gold, Game Pass and Game Pass ultimate.
Xbox Live is just needed to play online and Xbox Live Gold is just there to get additional discounts on games, The Game Pass is there for you so that you can download and play various game titles such as Gta 5, Afk etc. ( the games are only playable if the Game Pass is active) and then there's Game Pass Ultimate, which is there to play the games that are in the Game Pass (are almost 250) and there's also Xbox Live Gold in the pass inside and you get discounts. Hope I could help you with that.
So if I buy the Xbox Live Gold card now, for example, can GTA no longer be played because the Game Pass is still required here?
If you have Gta in the Game Pass then you need the Game Pass to play the game, which means you have to buy xbox credit and extend the Game Pass subscription